Monday, December 27, 2010

Fuels from Biomass Without the Microbes? Enzymes Triumphant

Virginia Tech researchers have been developing their enzymatic approach to advanced biofuels - from - biomass for some time. They believe that enzymes - without - the - microbe can provide a more efficient and stalwart production system. Their latest:

The research will be published in the January 2011 issue of the journal Chemistry & Biology.

"Enzymes self-assemble a cell-free synthetic pathway; that is, we can put the desired biological reactions to work without the other complex interactions that take place within a cell," said Y.H. Percival Zhang, associate professor of biological systems engineering at Virginia Tech.

"In microbial fermentations, glucose serves as both a growth substrate and a source of energy for generating a reduced power -- NADPH. In fact, only a small fraction of glucose is allocated to NADPH generation," he says. "The cell-free synthetic pathway process increases efficiency and reaction rate."

"By using an enzyme cocktail consisting of 12 purified enzymes and coenzymes, this work has also demonstrated that the enzyme cocktail systems can work in the presence of microorganism-toxic compounds from dilute-acid pretreated biomass, suggesting that enzyme systems do not require high-purity substrates for biotransformation," said Zhang. "In other words, after pretreatment, we can do bioconversion directly, followed by chemical catalysis," he said.

The article, "Biohydrogenation from Biomass Sugar Mediated by in vitro Synthetic Enzymatic Pathways," was written by Yiran Wang, research scientist in biological systems engineering at Virginia Tech; Weidong Huang, visiting scholar from the University of Science and Technology of China; Noppadon Sathitsuksanoh and Zhiguang Zhu; biological systems engineering Ph.D. students at Virginia Tech; and Zhang. _Physorg

The trend in advanced biofuels production has always pointed toward an eventual "acellular" approach, at least for small-scale, portable applications. Microbes are self-reproducing, and fairly easily "tweaked" genomically, but they can be a bit finicky when faced with some of the noxious process chemicals in common use today. Advanced catalysts -- eventually nano-molecular catalysts that are much more hardy than peptide enzymes -- will be designed to tolerate a wide range of reactants, products, intermediates, and impurities.

The researchers at VTU assume that their hydrogen will be used in hydrogen fuel cells. That is likely to be true at some scale, but hydrogen is quite valuable in its own right for a multitude of chemical and biofuels processes. It is more likely that most of the hydrogen will be used to produce more advanced biofuels, chemicals, plastics, other materials, feeds, etc.